Panadapter, the continuing story

13/09/2015 / ea3hoe / 0 Comments

So recently i got a new toy in the shack. I wanted to make a small step up from the RTL-SDR adapter and got myself an SDRplay. I first tried out the SDRplay using it as a plain SDR device and i must say that the guys at SDRplay did a great job. The radio is so much more sensitive than the RTL adapters (yes, also more expensive, i know) and this increased sensitivity really makes a difference. Also i can see 8MHz of band where the RTL adapter only (ONLY?) can see 3.2MHz. The SDRplay shows less spikes, less images, etc, etc. All in all simply a better radio.

Next step is to use the SDRplay as a panadapter for my TS-590. Since i have built the RTL-based panadapter described here i have been reading up a lot on where to connect the SDRplay. As you know the RTL adapter is connected to the first IF and that solution has a couple of issues:

I can only listen to the adapter on the IF frequency. This is not an issue when using Windows, i can use omni-rig to sync the SDR with the radio, but it is on the Mac. There is no omni-rig on the Mac.

I can only listen to the frequency the TS-590 is set to plus or minus 1 Mhz (something around there, i’m not sure how much bandwidth the IF shows).

Reading up on the web and looking at several different panadapter setups i found out that the IF solution i chose is not the most common one. The most common places to pick the signal for the panadapter is at the end of the RX path. CN101 and CN201 are the places where people pick their RX signal from where CN101 is before the BPF and CN201 is after. So i decided to use CN101. I created a jumper cable from an old Wifi antenna cable and hooked it up to an old jumper i had lying around. The shield of the cable i connected to ground exactly as shown on the image here. In fact, i took the idea from the website linked by the image.

Good things i found out:

I can really see 8 Mhz of spectrum now. Quite impressive although for HAM radio use i normally set the SDRplay to 1,5 MHz which usually covers the band i work at that moment.

I can use the SDR even with the radio switched off. Basically the SDR is now directly connected to the antenna and the antenna works whether the radio is switched on or not.

I can see other bands than the band i am working on. So i can work one band using the RTL adapter and in the mean time monitor the propagation on other bands to see if i need to move.